It’s meant to be polite, sort of like saying excuse me when interrupting your elders or two people in conversation.
I use it out of respect to the FReeper making the post.
The courtesy comment line is also used to differentiate between the FReepers post and my thoughts.
Ah, that makes sense. It sounds like you use “Courtesy Comment” the same way I like to use “Listen up, Beeeeeyatches!!!”